Impregnated pencil lead



Patented Sept. 4, 1951 IMPREGNATED PENCIL LEAD Charles H. Van Dusen,Jr., Willoughby, Ohio, and

Oscar E. Weissenborn, Verona, N. J., assignors toAddressograph-Multigraph Corporation, Cleveland, Ohio, a corporation ofDelaware No Drawing. Application August 8, 1946,

Serial N0. 689,195

Claims. 1.

This invention relates to a planographic imageforming pencil for use informing images upon master planographic printing plates includingaluminum and paper or like cellulose base master planographic printingplates.

A number of problems are encountered in the manufacture of planographicimage-forming pencils which are peculiar to such pencils and which arenot encountered in the manufacture of common "so-called lead pencils.Among these problems are: A planographic image-forming pencil must becapable of forming an inscription or image which will produce asatisfactory number of copies from the master plate upon which the imageis written; it must be capable of making uniform lines, that is to say,lines which are of substantially uniform width throughout their entirelength upon the master plate; the writing instrument, that is to say,the cylindrical rod or so-called lead which is embodied in such aplanographic pencil must be neither too soft so that the inscription orimage formed thereby will wash off the plate readily or so that it willproduce lines which will vary in width as the pencil moves across amaster aluminum or paper or like planographic plate on which it is beingused to write an image, and it must not be sufficiently hard to scratchsuch a masterplanographic printing plate; and it must have goodink-receptive and ink-retentive properties so that it will be receptiveto and will retain the lithographic inks used in making reproductionsfrom the master plate.

Accordingly, an object of the present invention is to provide a new andimproved image-forming planographic pencil embodying a writinginstrument or so-called lead which has good imageforming properties andwhich will produce images having good ink-receptive and ink-retentiveproperties for planographic or lithographic inks; which is sufficientlyhard to enable it to make lines of uniform width upon a paper or otherplanographic printing plate and to prevent the image made thereby fromwashing off the plate; and which is otherwise a satisfactoryimageforming planographic pencil.

An additional object of the invention is to provide a novel impregnantfor impregnating the cylindrical writing rods or so-called leads of thenew planographic pencil so as to impart thereto good image-formingproperties and so as to enable it to form images which have goodinkreceptive and ink-retentive characteristics.

Another object of the invention is to provide a novel method for makingthe cylindrical writ- 2 ing rods or so-called leads of the newplanographic pencil.

Other and further objects of the present invention will be apparent fromthe following description and claims which describe preferredembodiments of the invention and the principles thereof and what we nowconsider to be the best mode in which we have contemplated applyingthose principles. Other embodiments of the invention embodying the sameor equivalent principles may be used and changes may be made as desiredby those skilled in the art without departing from the present inventionand the purview of the appended claims.

In the practice of .the present invention the base of the cylindricalwriting instrument or rod or so-called lead which is embodied in the newplanographic pencil may be any oneof various compositions employed inmaking conventional hard or so-called 8H lead pencils. .Suchcompositions are illustrated, for example, in U. S. Patent No. 1,937,105and in The Chemical Formulary, vol. 2, page 268. Thus a typical formulawhich may be employed in preparing the base of or so-called lead for thecylindrical rod or writing instrument which is embodied in the newplanographic pencil may be that which is shown in the following example:

Example N0. 1 g Parts by weight Clay (binder) 5 to 8 Amorphous orso-called Mexican graphite 3 Carbon black 1 In the manufacture of thenew planographic pencil the base of the writing instrument orcylindrical rod which is embodied therein, and which may be preparedaccording to the formula set forth in the foregoing Example No. l, oraccording to any other suitable formula, is mixed with water to formaplastic mass or dough which is then extruded in rod form and dried andbaked or ignited in a graphite crucible in an oven at atemperature ofapproximately 1000 C. for approximately an hour;

The cylindrical rods or so-called leads thus prepared are thenimpregnated with a novel impregnant of the present invention, and for asuitable length of time, such as two hours, so as to impartimage-forming and ink-receptive properties to the rods or so-calledleads. This is accomplished by heating the rods for approximately fourhours in a kettle or other suitable container with one of theimpregnants which may be used in the practice of the present inventionand which im- 3 pregnant is preferably the varnish having thecomposition set forth in the following example:

Example No. 2

Parts by weight China-wood oil 50 Rosin 50 comes the tendency of theChina-wood oil if used J alone to bleed to the surface of the pencil.

During the operation of impregnating the rods or so-called oil-rosinmixture set forth in the foregoing Example No. 2 the temperature of the"impregnating solvent was maintained at about 200 0., care beingexercised to keep the temperature of. the impregnating mixture below thetemperature at which the China-Wood oil will polymerize and which isabout 275 C. During this operation the rosin dissolves in the China-woodoil to form an impregnating solution of rosin dissolved in China-woodoil. After the cylindrical writing rods or so-called leads were thusheated for about four hours in the China-wood oil-rosin impregnatingmixture they were removed from the kettle and allowed to cool toatmospheric temperature. The thus impregnated leads or rods were thenencased or enclosed in grooved wooden pencil casings in a conventionalmanner. This operation, as is well understood in the art, includesinserting the rods or so-called leads into a groove formed in one of twocomplementary sections of a wood or like pencil casing, adhesivelysecuring the two complementary halves or sections of the pencil casingtogether with the rod or so-called lead therebetween; suitably shapingthe outer surface of the pencil casing as by forming hexagonal facesthereon; and then suitably finishing the pencil casing as by sanding andpainting the same.

In place of the preferred China-wood oil-rosin impregnant set forth inthe foregoing Example No. 1 we may use, with less satisfactory results,certain other greasy planographic image-forming materials as theimpregnant and among these are the following: (a) China-wood oil alone;(b) rosin alone; a mixture of about equal parts of China-wood oil andCarnauba wax, by weight; and (d) a mixture composed of about equal partsby weight of China-wood or tung oil and a heat-reactivephenol-formaldehyde resin. Likewise, in place of a selected one of thegreasy planographic image-forming materials referred to above, we mayemploy as the impregnant selected non-greasy image-forming materialssuch, for example, as certain of those disclosed in United States PatentNo. 2,342,713,'granted February 29, 1944, and including a mixture ofone'part of Nigrosine base black and three parts of tricresyl phosphate,by weight. It has been found that the new planographic pencil preparedaccording to the present inven- 4 tion has good image-formingproperties, and that images formed thereby have good ink-receptiveproperties for lithographic inks, which are imparted thereto by thenovel impregnating solution hereinbefore described; that the writinginstrument or so-called lead embodied in the new lithographic pencil issufficiently hard to enable it to form good images, including lines ofuniform width, on paper and like planographic printing plates; that itwill provide images which will not readily wash off such plates; andthat it provides images which will enable satisfactory editions ornumbers of copies to be reproduced from a master paper or likeplanographic printing plate when the latter is employed in makingreproductions in a rotary offset duplicating or planographic printingpress or the like.

It will thus be seen from the foregoing description that the presentinvention provides a new and improved planographic pencil, and a novelmethod of making the same, and that the new lithographic pencil has thedesirable advantages and characteristics, and accomplishes its intendedobjects, including those hereinbefore pointed out and others which areinherent in the invention.

We claim:

1. A pencil lead impregnated with a mixture of China-wood oil and rosin.

2. A pencil lead impregnated with a mixture of China-wood oil and rosinin about equal parts, by weight.

3. A pencil lead comprised of amorphous graphite bonded with clay andimpregnated with a mixture of China-wood oil and rosin.

4. A pencil lead comprised of a mixture of amorphous graphite and carbonblack bonded with clay and impregnated with a varnish composed ofChina-wood oil and rosin.

5. A pencil lead comprised of a mixture of amorphous graphite and,carbon black bonded with clay and impregnated with a varnish composed ofabout equal parts, by weight, of Chinawood oil and rosin.

CHARLES H. VAN DUSEN, JR. OSCAR E. WEISSENBORN.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 447,310Goldsmith Mar. 3, 1891 551,288 Kaiser Dec. 10, 1895 1,411,822 Wehn Apr.4, 1922 1,732,420 Rice Oct. 22, 1929 1,937,105 Thomsen Nov. 28, 19331,970,603 Grossman Aug. 21, 1934 2,041,740 Beckman May 26, 19362,075,223 Pischel Mar. 30, 1937 2,162,311 Kreutzer June 13, 19392,238,771 Chesler Aug. 15, 1941 FOREIGN PATENTS Number Country Date146,806 Germany Nov. 12, 1903 23,054 Great Britain of 1914 478,239 GreatBritain Jan. 10, 1938 501,295 Great Britain Feb. 24, 1939 181,536

Switzerland Apr. 1, 1936

1. A PENCIL LEAD IMPREGNATED WITH A MIXTURE OF CHINA-WOOD OIL AND ROSIN.